loops - modifying and looping

What does for item in list: do?

• Deletes items

• Changes items

• Loops through each item

• Sorts list

Answer explanation

The statement 'for item in list:' is used to loop through each item in the list, allowing you to perform actions on each element. This makes 'Loops through each item' the correct choice.

Which method gives number of items in a list?

• size()

• count()

• length()

• len()

Answer explanation

The correct method to get the number of items in a list in Python is 'len()'. The other options, 'size()', 'count()', and 'length()', are not valid for this purpose.

What is the output?

nums = [1, 2, 3]

for i in range(len(nums)):

nums[i] += 5

print(nums)

• [1, 2, 3]

• [6, 7, 8]

• [5, 5, 5]

• [10, 20, 30]

Answer explanation

The loop iterates over each element in nums, adding 5 to each. After the loop, nums becomes [6, 7, 8]. Thus, the correct output is [6, 7, 8].

What is the purpose of range(len(list))?

• To loop through values

• To get indexes

• To reverse a list

• To sort a list

Answer explanation

The expression range(len(list)) generates a sequence of indexes for the elements in the list. This allows you to access each element by its index, making it useful for iterating through the list while knowing the position of each item.

What is the output?

data = ["a", "b", "c"]

for i in range(len(data)):

data[i] = data[i].upper()

print(data)

• ['a', 'b', 'c']

• ['A', 'B', 'C']

• ['A', 'b', 'C']

• Error

Answer explanation

The code iterates through the list 'data' and converts each element to uppercase using the 'upper()' method. Thus, the output will be ['A', 'B', 'C'], making this the correct choice.

Can you use for loop to modify a list directly?

• No

• Yes, with index

• Only with append
  

• Only with remove

Answer explanation

Yes, you can use a for loop with an index to modify a list directly. This allows you to access and change elements at specific positions within the list.

What is the output?

lst = [3, 6, 9]

for i in range(len(lst)):

lst[i] *= 2

print(lst)

• [3, 6, 9]

• [6, 12, 18]

• v

• Error

Answer explanation

The code iterates through the list 'lst' and multiplies each element by 2. The original list [3, 6, 9] becomes [6, 12, 18] after the operation. Therefore, the correct output is [6, 12, 18].

What will this code print?

nums = [2, 5, 8]

for n in nums:

print(n)

• 2 5 8

• 0 1 2

• 3 3 3

• Error

Answer explanation

The code iterates over the list 'nums' and prints each element. Therefore, it will print '2', '5', and '8' on separate lines, resulting in the output '2 5 8'. This matches the correct answer choice.

Which method is correct for modifying list values?

• list.append()

• list[i] = new_value

• list.sort()

• list.modify()

Answer explanation

The correct method for modifying list values is 'list[i] = new_value', which directly assigns a new value to the specified index. The other options either add elements, sort the list, or are invalid methods.

What is the output?

marks = [35, -5, 70]

for i in range(len(marks)):

if marks[i] < 0:

marks[i] = 0

print(marks)

• [35, -5, 70]

• [35, 0, 70]
  

• [0 ,0 ,0]

• Error

Answer explanation

The code iterates through the 'marks' list. When it finds a negative value (-5), it replaces it with 0. Thus, the final output is [35, 0, 70], making the correct choice [35, 0, 70].